What is the average speed for this lap?

ok, i am new at physics, so please no one make fun of me for my stupid questions. Ok here is the questions
In the Canadian Grand Prix Auto race, the drivers travel a total distance of 304.3km in the 69 laps around the track. If the fastest lap time was 84.12s, what is the average speed for this lap? express your answer in metres pers second and kilometres per hour.
Please someone help me, i have a test and i need some serious help!!!!!!!

You probably have an equation in your book or from your instructor that says [itex]speed_{avg} = \Delta distance / \Delta time[/itex]. You know the delta time for the lap, all you need is the distance of one lap. You can calculate that from the information in the problem statement.

i know i must be really stupid but i still dont understand, ok so i take thte 304.3km and divide it by 69 to figure hot long it takes to do one lap, but i first convert the 304.3km to metres which is 304300m, then i divide by 69, which is 4410..what units is that, do i have to do anything else..??

i know i must be really stupid but i still dont understand, ok so i take thte 304.3km and divide it by 69 to figure hot long it takes to do one lap, but i first convert the 304.3km to metres which is 304300m, then i divide by 69, which is 4410..what units is that, do i have to do anything else..??

Janelle, it doesn't matter if you do all your unit conversions in the beginning or at the end. What is important is that you are consistent with your units throughout. In other words, if you're more comfortable with km rather than meters, make sure everything that goes into your equation with some sort of distance unit is in km. At the end, if you have to give your answer in meters, you can convert km to meters then. The only rule is you can't use two different units in the same equation. So, if you needed to include two distances, you can't have one in meters and the other in km.